Personal information such as a telephone number, an e-mail address or the like is recorded to a portable terminal such as a cellular phone or the like. Moreover, portable terminals have been provided with credit card and electronic money functions resulting from recent enhancements of functions. Therefore, it is a serious issue that a portable terminal is left or stolen. Accordingly, it is proposed that a portable terminal is linked with another wireless device and position information of the portable terminal is transmitted to a predetermined communication destination if the portable terminal and the wireless device are separated from each other and the portable terminal is determined to be left.
Patent Document 1 discloses a mobile communication terminal that transmits its position information and restricts its functions when a signal from a communication terminal is no longer received.
However, a conventional portable terminal is locked the moment when a communication between the portable terminal and a child device becomes impossible. Therefore, the portable terminal is locked each time a user accidentally excessively separates from the portable terminal. As a result, the user has to release the locked terminal each time the portable terminal is locked, leading to heavy burdensomeness. Moreover, conventional technology only ensures security by locking a portable terminal when being left. Actually, it is necessary to prevent a portable terminal from being left.
Patent Document 1: Japanese Laid-open Patent Publication No. 2005-333626